1. Field of the Invention
The present invention relates to a sheet feed shaft to be used for feeding paper for example in a printing machine or in a printer for an office machine or for the feed of sheet such as a film in an overhead projector or the like, as well as an apparatus and method for manufacturing the sheet feed shaft.
2. Description of the Related Art
As to a sheet feed shaft to be used for the feed of paper in for example a printing machine or a printer for an office machine, as well as an apparatus and method for manufacturing the sheet feed shaft, the applicant in the present case has already proposed a sheet feed shaft and an apparatus and method for manufacturing the same in Japanese Patent Laid-Open No. Hei 10(1998)-203675 in which spike-shape projections are formed on the surface of a metallic rod.
More particularly, in the proposed sheet feed shaft manufacturing apparatus, as shown in FIG. 6, a V block 512 installed on a base 511 is used as a support base for supporting a metallic rod 51 as a workpiece, and the metallic rod 51 is lifted by a lifter 513 installed on the base 511. A collar 514 is wound round the metallic rod 51 to avoid direct contact of the metallic rod 51 with the lifter 513. A stock removing frame 515 is erected on the base 511 to prevent the metallic rod 51 after processing from being lifted in an engaged state with perforating edges 528 of a punch 524.
A split gear 517 is integrally mounted on a holding bush 516 which supports one end of the metallic rod 51, and is in mesh with a drive gear 519 of a stepping motor 518. The holding bush 516 is fixed to the metallic rod 51 with a screw 520. With power of an air cylinder (not shown) or the like, a tip end of a detent member 512 is engaged with the split gear 517.
A motor cylinder 522 is a multi-point positioning member whose tip end is put in abutment against one end of the metallic rod 51 through a magnet tip 523. A punch unit 524 is moved up and down by a press. A pair of perforating members 525 and 526 are fixed to the punch unit 524 with use of clamping means 527.
As shown in FIG. 7, stripe-shape arranged perforating edges 528 are formed in mutually opposed one surfaces of the pair of perforating members 525 and 526. The perforating members 525 and 526 are secured to the punch unit 524 by inserting the clamping means 527 into holes 529. As shown in FIG. 8, the pair of perforating members 525 and 526 are opposed to each other on the surface of the metallic rod 51 while maintaining a space settled previously corresponding to an outside diameter of the metallic rod 51. Likewise, the perforating edges 528 are opposed to each other on the surface of the metallic rod 51.
In the apparatus of such a structure, the punch unit 524 is moved up and down by a press, whereby the perforating edges 528 prick the surface of the metallic rod 51 in a successive manner to form spike-shape projections in an orderly arranged state and in directions contrary to each other.
In the conventional sheet feed shaft manufacturing apparatus, however, a support base for supporting the metallic rod 51 as a shaft body is needed. Besides, the V block 512 as the support base has a pair of support portions 512A for supporting the metallic rod 51, so that projections cannot be formed on the surface portions of the metallic rod 51 corresponding to the support portions 512A. Thus, portions free of projections remain on the metallic rod 51, that is, it is impossible to form projections throughout the whole surface of the shaft. Such an inconvenience can be avoided by processing the projections-free portions again through the same process as above to form projections. In this case, however, there arises an inconvenience such that the projections already formed are crushed by the support portions 512A. Thus, it is extremely difficult to form projections throughout the whole surface of the metallic rod 51.
Moreover, in the above conventional manufacturing apparatus, perforating edges 528 are provided on only the upper side and only the upper side of perforating edges 528 cut into the surface of the metallic rod 51 in a successive manner, going around the outer periphery of the metallic rod 51 to form a group of projections, thus giving rise to the problem that a long processing time is required.
Further, when the sheet feed shaft machined by the conventional manufacturing apparatus is applied to a printing machine and the size of sheet to be fed is changed, projections are not symmetric with respect to the newly-fed sheet, so that a non-uniform force is exerted on the sheet feed, giving rise to such an inconvenience as the sheet being fed in a distorted state.
More particularly, according to a certain change-over method for changing the sheet size from one to another, it is not determined unambiguously to which position of the shaft the sheet corresponds, so there occurs a case where projections are not symmetric right and left with respect to the sheet, thus resulting in that the sheet feeding force becomes non-uniform and the sheet being fed is distorted.